Magnetic recording and reproducing apparatus using an endless spirally wound magnetic tape



Dec. 13, 1949 5 J BEGUM 26,490,771

MAGNETIC RECORDING A ND REPRODUCING APPARATUS USI AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE Filed Sept. 6, 1945 8 Sheets-Sheet l INVENTOR. .SFM/ JOSEPH EEGZ/N Dec. 13, 1949 5. J. BEGUN 2,490,771

MAGNETIC RECORDING AND REPRODUCING APPARATUS USING AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE 1945 8 Sheets-Sheet 2 Filed Sept. 6

INVENTOR BY M5 MM 8 MLL- -AU Semi ATTORNEY 8 Sheets-Sheet 3 INVENTOR. 5 J 5EGU/V M mwa/ S. J. BEGUN REPHODUCING APPARATUS USI AN ENDLESS sPIRALLY WOUND MAGNETIC TAPE mm Q5 @w] E A MAGNETIC RECORDING AND DH uli l Dec. 13, 1949 Filed Sept 6, 1945 Dec. 13, 1949 5. J. BEGUN 2,490,771 MAGNETIC RECORDING AND REPRODUCING APPARATUS USING AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE 8 Sheets-Sheet 4 Filed se i. 6, 1945 INVENTOR. 36 SEM/ J050H 555m BY I S. J. BEGUN ECORDING AND REPRODUCING APPARATUS USIN Dec. 13, 1949 MAGNETIC R AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE 8 Sheets-Sheet 5 Filed Sept. 6, 1945 INVENTOR SEM/ JOJE H SEGA/N ATTORNEY Q a ob MN t Dem 1949 s. J. BEGUN 2,490,771

MAGNETIC RECORDING AND REPRODUCING APPARATUS USING AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE Filed Sept. 6, 1945 a Sheets-Sheet cs $"20 v "80 n //M INVEST; WQw

ATTORNEY Dec. 13, 1949 5. BEGUM 2,490,771

MAGNETIC RECORDING AND REPRODUCING APPARATUS USING AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE Filed Sept. 6, 1945 I 8 Sheets-Sheet 7 326 I N VEN TOR.

\SeI m JZasep/r Begun BY 3W may A TTORNEY Dec. 13, 1949 5 BEGUM 2,490,771

MAGNETIC RECORDING AND REFRODUCING APPARATUS USING AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE Filed Sept. 6, 1945 8 Sheets-Sheet 8 IN V EN TOR.

SemIJBSP oh Begun BY S W Y... 51

ATTORNEY Patented Dec. 13, 1949 MAGNETIC RECORDING AND ING APPARATUS USING REPRODUC- AN ENDLESS SPIRALLY WOUND MAGNETIC TAPE Semi Joseph Begun. Cle slg'nor to Magnetone,

corporation of Ohio veland Heights, Ohio. as-

Ine., Cleveland, Ohio,

Application September 6, 1945, Serial No. 814,709 28 Claims. (Cl. 179-1002) This invention relates to magnetic recording and reproducing devices, and more particularly to such devices utilizing an endless spirally wound magnetic tape coil as a recording medium.

Among the objects of the invention is a novel magnetic recording device of the foregoing type, which is free from the difnculties inherent in all prior endless spiral coil magnetic tape recording devices, as well as various other improvements in magnetic recording devices. A distinct important phase of the invention involves a magnetic recording device of the foregoing type in which the endless tape coil is combined with a detachable holder unit arranged for detachable coupling interconnection with a separate drive unit, such as a tum-table drive of a standard phonograph.

The foregoing and other objects of the invention will be best understood from the following description of exempliflcations thereof, reference heing had to the accompanying drawings where- Fig. 1 is a vertical sectional view illustrating a magnetic tape recording device exemplifying one form of the invention;

Fig. 2 is a plan view of the principal elements of Fig. 1;

Fig. 3 is a front view of some of the elements of Fig. 1;

Fig. 4 is an end view bers of Fig. 1;

Figs. 5 and 6 are side views of diiferent modiilcations of the guide member of Fig. 4;

Fig. 7 is a portion of the coil guide structure of the type shown in Fig. 1;

Fig. 7A is a cross-sectional view of a metallic magnetic record tape;

to Fig. 2 illustrating of one of the guide mem- Fig. 8 is a plan view similar a modified form of device exemplifying the invention;

Fig. 9 is a view similar to Fig. 2 illustrating a modified form of some of the elements of a device. such as shown in Fig. 1;

Fig. 10 is a partially cross-sectional and partially elevatlonal view of another form of endless tape coil recording device exemplifying the invention;

Fig. 10A is a cross-sectional view along line IOA-IIA of Fig. 11;

Fig. 11 is a top view of the device of Fig. 10;

Fig. 12 is a vertical sectional view illustrating another form of magnetic tape recording device exemplifying the invention;

Fig. 13 is a plan view of some of the elements of Fig. 12;

Fig. 14 is an elevational view of one of the aligning rollers along line l4il of Fig. 13;

Fig. 15 is a view similar to Fig. 1 illustrating another form of magnetic recording device exemplifying the invention;

Fig. 16 is a front view of some of the elements of Fig. 15;

17 is a Fig. 15;

Fig. 18 is an end view of Fig. 15;

Fig. 19 is a cross-sectional view illustrating a guide structure element;

Fig. 20 is a cross-sectional view along line 28- 28 of Fig. 19;

Fig. 21 is a cross-sectional view along line 2|- II of Fig. 19;

Fig. 22 is a view similar to Fig. 19 ot a modified form of guide member arrangement;

Fig. 23 is a plan view 01' the guide member of Fig. 22 and its relation to the cooperating elements;

Fig. 24 is a plan view of another form of recording device exemplifying the invention, with its cover removed;

Fig. 25 is a cross-sectional view along line 3-25 of Fig. 24;

' Fig. 26 is a detailed cross-sectional view of some of the elements of Fig. 24 along line 2826 thereof.

Fig. 27 is a detailed sectional view of some of plan view of some of the elements of of some of the elements the elements of the device shown in Figs. 24 and 25;

Fig. 28 is a view similar to Fig. 24 of a modified form of recording device of the type shown in Fig. 29 is a cross-sectional view along line 28-29 of Fig. 28; and

Fig. 30 is a cross-sectional view along line 38-80 of Fig. 28.

Various efforts have been made in the past to provide a commercially practical magnetic sound recording and reproducing device utilizing an endless magnetic signai carrier One type of such device, in which such endless magnetic sound carrier is wound in the form of an endless helix around a plurality of spaced guide rollers, is now commercially available and finds great appeal among singers, speakers, actors, and students of elocution and foreign languages desiring to hear their voice or speech.

However, although there has been existin an urgent need for a much simpler and more compact endless magnetic tape recording and reproducing arrangement in which the endless magnetic signal carrier tape is wound in the form of a compact spirally wound coil, no commercially practical arrangement of this type has hereto been available. Such compact spirally coiled endless magnetic tape recording arrangement is particularly desirable for use in connection with devices, such as disc recording and phonograph devices, especially if such endless magnetic tape recording arrangement could be made in the form of readily interchangeable units adapted for operation by the standard drives of conventional turn-tables of disc phonographs or disc recording An endless magnetic tape recording and reproducing arrangement exemplifying one form of the invention will be described in connection with Figs. 1, 2 and 3.

The endless magnetic signal carrier is formed friction between the convolutions of the tape coil prevented, if the lower edges of the tape coil convolutions 2i are held in a generally horizontal position in suillcient frictional engagement with a rotating surface of an underlying revolvably mounted disc member til which is driven at sufficiently high speed so that the rotating disc 30 acts as a convolution expanding member which subjects the lower edges of the tape coil convolutions to frictional forces which tend to expand and loosen them in outward direction, and thus counterbalance the slippage friction forces which tend to contract and tighten the tape coil convolutions in inward direction.

of a thin tape 20 which is wound into a spiral coil 2| with the innermost convolution 22 connected to the outermost convolution 23- by .a cross-over loop 24 which is guided so as to move with the required clearance above the spiral coil convolutions 2|.

For satisfactory recording and reproduction of sound, or similar signals, the endless magnetic tape 2. has to be impelled through the magnetic head 25 at a uniform speed, and each portion of the endless tape 20 must move with the same linear velocity regardless of whether it is a part of an inner or outer convolution of the spiral coil 2i. Since the outer convolutions have a longer periphery, each outer convolution of the tape coil 2| must, therefore, move with greater angular velocity than the adjacent inner coil convolution. As a result, adjacent convoiutions of the tape coil 2i must continuously slip past each other, and if they are permitted to remain in actual physical contact, friction between the coil tape convolutlons will take place.

The frictional slippage forces which are thus developed between adjacent coil convolutions as a result of their uniform speed linear motion, in the direction from the outer convolution 23 to x the inner convolution 22 of the tape coil 2|, tend to contract and thereby tighten the individual convolutions. If such spirally wound tape coil is made with more than a few convolutions, the

; contracting and tightening of each convolution increases the frictional forces exerted on the adjacent inner convolutions, and they in turn increase the contraction and tightening actions their cumulative effect creates abnormally large stresses which stop the motion of the tape 20 or damage it. These difilculties made it heretofore impossible to construct a commercially practical magnetic recording device of the foregoing type having enough tape coll convolutions for making records of the length usually required from a practical recording device.

According to the invention, the foregoing difflculties are overcome by so guiding the linearly impelled convolutions of such spirally wound magnetic tape coil recording arrangements, as to subject them to forces which tend to expand and separate and loosen the individual tape coil convolutions, and thus counteract the convolution contracting and tightening forces.

I have found that in an endless magnetic tape recording arrangement operating with a spirally wound magnetic tape coil of the type shown in Figs. 1 and 2, even when using a very thin tape of permanently magnetizable steel, having a thickness of the order of only three thousandths of an inch, the adjacent linearly impelled convolutions of such coil may be kept in the required Figs. 1 to 3 show one practical form of a guiding and driving arrangement for such spirally coiled endless tape recording device.

The convolutions 'of the substantially flat compact tape coil 2| are held and guided in horizontal operating positions by the upwardly facing outward surface region of a revolvably mounted and generally horizontally extending circular disc 80. which serves as a coil guiding member.

The inner convolution is guided by the periphcry of the revolvably mounted inner disc roller 3i and revolvably mounted cross-over and alignment rollers 32, 33, respectively, which are so positioned that when the tape is impelled at a uniform linear speed in the direction of the arrow 26, the tape elements of the inner convolution 22 are continuously withdrawn from its inner position within the coil 2i and moved over the periphery of the inner revolvably mounted guide memberor roller Si in an upwardly inclined direction along the cross-over loop 26 toward the cross-over roller 32 so as to clear the tape coil 2 i, and therefrom over the ent roller 33 in a tangential direction to the starting point of the outer coil convolution 23, while the edges of the tape coil convolutions 2i maintain engagement with the underlying tape guide and ending disc 3d. The tape guide disc 30, the inner tape roller 3i and the cross-over and alignment rollers 32, 33 are held in the required revolving operating positions by a suitable holding structure, such as suitably shaped rigid mounting or holder bar 35. The alignment roller 32 may be omitted. if the cross-over roller Si is mounted in an inclined position, so that the part of the cross-over loop 2t extending from the inner convolution is kept by one side of its grooved tape guide rim clear from the tape coil convolutions 20, while its other side is aligned opposite the starting point of the outer tape convolution 23.

The linearly impelled convolutions of the endless tape coil 2| are held in their horizontal operating position in engagement with the underlying surface of the tape coil expan disc It by a plurality of elongated guide members 4i held in a generally radial direction above peripherally displaced portions of the spiral tape coil 2|. The guide members ii are so arranged and positioned as to prevent the convolutions of the tape coil from climbing from their normal operating position.

In the form ofthe invention shown in Figs. 1 and 2, four tape coil guide members are used, and they are held in their operating position by portions of the elongated holder bar 34 overlying the tape coil convolutions .and by two of its two cross arms 35, 36. Each guide member 4! is held in its position above the tape coil 2! by two upwardly projecting studs 42 having threaded ends loose condition, and harmful excessive slippage is engaging internally threaded holes of adjusting screws 43 rotatably held by nuts 44 in holes of a mounting plate 45. The mounting plate 45 is shown secured, as by screws, to the underside of the holder bar 33 which is provided with holes within which the heads of the adjusting screws 43 are confined.

By turning the heads of the adjusting screws 43, the level of the lower edge of each guide member 4| may be adjusted to assure that the lower edges of the convolutions of the tape coil 2| remain in their position in which they maintain frictional engagement with the underlying surface of the tape coil guide disc 30.

As shown in the transverse cross-sectional view, Fig. 4, of the guide bar 4|, its lower side is rounded so as to confine its engagement with the adjacent edges of the tape coil convolutions to a very small area and reduce to a minimum the friction developed at the engaging surfaces. By mounting on one side of the guide bar 4| a spring strip of non-magnetizable metal, or brush-like layer 43 of elastic non-magnetic bristle-like filaments, so that its lower edge lightly engages the upper edges of the tape coil convolutions 2| without exerting thereon excessive pressure, it is possible to maintain the lower edges of the tape coil convolutions 2| in good frictional engagement with the underlying tape expanding disc while keeping the guide bar which its lower edge is spaced by a slight gap from the upper edges of the tape coil convolutions 2|.

In order to eifectively counterbalance the convolutions contracting and tightening effect of the slipp ge friction forces between the adjacent linearly impelled tape coil convolutions 2|, the underlying coil expanding disc 30 should not only maintain frictional engagement with their lower edges but it should also be rotated at a greater speed than the linear speed at which the tape 23 is impelled along it. With a given magnitude of the frictional engagement, the expanding forces imparted by the rotating disc to the tape coil convolutions engaged thereby will be determined by the magnitude of the difference by which the speed of the expanding disc portion exceeds the linear speed of the tape convolution engaged thereby. The greater this excess of speed is, the greater the expanding forces imparted by the rotating disc to the tape convolution engaged thereby.

Since the linear speed of all tape coil convolutions is uniform, and the speed of the underlying disc surface portions increases with the diameter of the convolutions, each successive outer convolution coupled to such rotating expanding disc is subjected to increasingly larger expanding forces. As a result, such arrangeemnt will keep all convolutions of the tape coil 2| loose and the slippage forces between adjacent convolutions are reduced to a negligible value and they do no harm.

If the tape expanding disc is rotated at a willciently high speed, the expanding forces imparted by its periphery to the tape convolutions coupled thereto will cause the tape coil to expand in outward direction. Excessive expansion of the tape coil 2| under such operating conditions may be prevented by providing the outer ends of the tape uide bars 4| with downwardly extending stop projections 43, as maximum outward expansion of the tape coil 2|.

In general, it is suflicient to rotate the tape expanding disc 30 with a speed which, withoutoverbalancing contracting effect of the slippage fricshown in Fig. 5, for limiting the l 4| adjusted in a position at tion forces, is sumcient to reduce them to a magnitude at which the convolutions of the tape coil are maintained in a loose condition and excessive slippage friction does not develop. Under such operating conditions, the tape coil 2| may tend to contract. Since the angular velocity of the rotating disc, which determines the magnitude of the expanding forces exerted by its surface on the tape convolutions is reduced as the diameter of the tape coil is reduced, it may be desirable to prevent the excess contraction of the tape coil convolutions.

Such excessive contraction of the tape coil 2| may be prevented by providing the inner end of each guide bar 4| with a stop projection 48 in the way shown in Fig. 6, for instance.

A uniform operating speed through the magnetic head 25 may be imparted to the tape 23 by applying a rotary driving force either to the cross-over roller 32 or to the tape coil expanding disc 30. If the rotary driving force is applied to the cross-over roller 32, the linearly driven crossover loop 24 imparts a rotational movement to the tape coil 2| and through the frictional coupling engagement of its lower convolution edges to the underlying tape expanding disc 3|I, the latter is rotated at an angular speed at which its peripheral portion engaged by the inner coil convolution 2| is at least equal to the linear speed of said inner convolution 2|. The diameter of the inner coil convolution and its speed may be determined by the inner stop projections 43| of the guide bars 4 I, such as shown in Fig. 6.

In the arrangement shown in Figs. 1 to 3, the circular rim 5| of the inner tape coil disc roller 3| serves as the inner boundary of the spiral coil 2|.

The inner convolution withdrawn from its the inner rim 5| of 22 of the tape coil 2| is position of engagement with the inner coil roller 3| at a tangential direction from a point close to the place where one of the guide bars 4|, in the case shown, the guide bar underlying the cross arm 36 keeps the tape coil confined in its space above the disc 30 so as to assure that the inner tape convolution 22 is guided properly from the space within which the tape coil 2| to the higher level of the cross-over roller 32.

In a similar way, the other side of the crossover loop 24 reaches tangentially its position. in the outer tape coil convolution 23 at a place where the coil is held confined along the disc 33 by guide bar 4| underlying the other cross arm 35.

Since the inner convolution 22, in passing from the coil must rise gradually in tangential direction from its position on the inner rim 5| along the cross-over loop 24 to the cross-over roller 32, the portion of the inner rim 5| along which the inner tape convolution 22 gradually rises must be kept free and the facing portion of the tape coil 2| must be deflected therefrom.

In the form of arrangement shown in Figs 1 to 3, this is accomplished by mounting immediately adiacent the guide bar 4|, at the place where the inner tape convolution 22 starts to rise, and leaves its tangential engagement with the rim 5| of the inner coll roller 3 I, two deflecting pins 53 extending downwardly to near the surface of the tape disc 33 for keeping the coil convolutions 2| away from the rim portion of the inner coil roller 3| from which the inner coil convolution 22 extends, and thus provide the necessary clearance between the coil convolutions 2| and the overlying bridging loop 24.

portion of the cross I have found that a tape coil arrangement of the type shown in Figs. 1 and 2, using a flat steel tape only three mills thick driven by an underlying tape expending disc 30 driven at 18 revolutions per minute and having an inner coil roller 3|, ten inches in diameter, arranged in the way shown in Figs. 1 and 2, will impart to the outer convolutions of a tape coil 2 I, sufllcient outwardly expanding forces as to automatically expand the coil to a position in which the cross-over loop 24 is kept sufliciently tight for maintaining good coupling engagement between the cross loop 24 and the cross over roller 32, if the latter is used to drive the tape at the desired operating speed. Any form of drive may be used for imparting the rotary driving motion to either the tape expanding disc 34 or to the cross-over roll 32. The spiral magnetic tape coil arrangement of the invention shown in Figs. 1 to 3 is designed so that it may be driven by a standard drive of the type used for driving disc phonograph or disc recording machines. Thus the revolvable elements of the magnetic coil guide and driving arrangement, such as shown in Fig. 1, may be revolvably mounted on a turn-table board of a conventional disc phonograph either on the top or on the underside thereof, without interferring with its use for playing or making disc records.

In the form shown in Figs. 1 and 2, the drive and guide elements for the endless spirally wound magnetic recording tape arrangement is designed in the form of a detachable coil holder unit which may be placed on the top of a standard disc type phonograph for coupling either the tape expanding disc 30, or the cross-over roller 32 to the motor driven turntable of the phonograph, so that it may be driven thereby, in the same way as a conventional phonograph disc is driven during a reproducing or the record cutting operation.

In the drawings, a conventional turntable disc 8|! is shown fixed to a vertical turntable shaft 6| which is revolvably mounted in a bearing housing 62 suitably held below the turntable board 63 of a conventional phonograph or radio cabinet. The turntable disc 60 may be rotated at the standard speed, for instance, 78 revolutions per minute, by

a any conventional motor drive, such as a motor 64 having a rubber surfaced driving pulley 65 which is pressed against the surface of the rim of the turntable disc 60, so as to rotate it at the required speed. The expanding disc of the tape coil drive and guide arrangement has a central hole 61 and a circular row of coupling holes 63 so that by placing it on the turntable disc 60 it is instantly coupled thereto in the same way as a phonograph disc.

The center portion of the tape expanding disc 30 is provided with an upwardly projecting hollow shaft section I I, which is revolvably mounted in a bearing bracket I2 suitably secured to the underlying portion of the holder bar 34. The upper end of the hollow disc shaft 1 I is retained in its revolving position within the bearing bracket 12 by a nut 14, so that when the holder bar 33 is lifted, the tape expanding disc 30, the tape coil 2|, and the other elements held thereon will be lifted from their position on the phonograph top.

The cross-over roller 32 may be revolvably held either on the cross bar 34, as shown, or may be mounted on a shaft projecting upwardly from the phonograph top board 63, in which case, the

cross-over loop is slipped into the peripheral guide groove of the cross-over roller 3| after the tape coil holder bar 33 with the coil guiding and driving arrangement has been placed in the opcoma eratlng position on the turntable disc 80. By I mounting the cross-over roller 32 from the coil holder bar 34, on which the other elements of the magnetic tape drive are mounted, the operation of removing or coupling the tape coil holder unit on the phonograph board is simplified.

In the form shown in Figs. 1 and 2, the crossover roller 32 is revolvably held by the lower flanged portion of a hollow shaft section 15 which is held aflixed within the hole of a mounting bracket 16 by a nut 11 engaging the upper end of the hollow shaft section 15, two upwardly projecting threaded studs 18 extending from the mounting bracket 16 of the cross-over roller 32 held by nuts 8| extending across a longitudinal channel 19 of the holder 34 and are clamped in the adjusted position by a nut collar fitting into the recessed wall portion 82 of the coil holder 34. By loosening the nuts 8|, the mounting plate IS with the cross-over roller 3| may be longitudinally shifted along the slot 19 and the tension of the endless tape coil 2|, adjusted so that after the desired adjustment is made, the mounting plate with the cross-over roller 3| are clamped in the adjusted position.

As shown in Figs. 1 and 2, the magnetic head is carried by a bracket 85 having a longitudinal slot 96 engaging a stud 81 projecting downwardly from the mounting bar 34 and being held thereon by a nut, so as to permit adjustment of the magnetlc head in its proper engagement with the portion of the cross-over loop of the endless tape passing therethrough. If the cross-over roller 32 is used for driving the tape 20 at uniform speed, it may be combined with a coupling disc 99, which as indicated in dotted lines, forms in conjunction with the crossover roller 32 a unitary stru ture similar to the expanding disc 30 designed for ready coupling to the turntable disc 60, the lower surface of the couplingdisc 89 being on the same level as the lower'surface of the tape expanding disc 30. With such arrangement, the endless coiled magnetic recording tape coil driving and guiding unit, having all its elements operatively combined into a unitary'structure, may be coupled in an operative position on a standard phonograph table so as to drive the tape by coupling the turntable disc 69 either to the tape expanding disc 30 or to the cross-over roller coupling disc 89.

As shown in Figs. 1 and 2, the holder bar 34 has a downwardly projecting register pin 9| fitting into an opening of a register socket 92 suitably held on the phonograph board 63, so as to assure that when the top holder bar 34, which is placed in its operative position on the phonograph board 63 and the tape drive is coupled to the turntable disc 60, the coil holder bar 34 will remain stationary.

The coil holder bar 34 is also provided with an electric connector member 93 arranged to make detachable connection with a connector member 94, located on the phonograph board 63, whenever the coil holder 34 is placed thereon in its operative position. Any suitable known readily engageable and disengageable electric connector arrangement, such as plug and socket connector arrangements, may be used for this purpose. In the form shown, the connector member 93 is combined with the register pin 9| and has a plurality of contact springs 95 which engage a plurality of contact strips 96 held by the cooperating connector member 94 which is combined with the register socket 92. The connector members 95, 96 serve to complete the operating circuits from the elements of the magnetic head and to the amplifier and all other control elements used for recording and from the endless tape coil 2| in the way described, for instance, in my corresponding application Serial No. 340,030, filed June 12, 1940, now Patent No. 2,856,146, dated August 22, 1944, in connection with Figs. 1 to 11. With such arrangement, the operating circuits required for controlling the recording and reproducing operations carried on by the endless coiled magnetic recording tape 2| of the holder 24 are automatically established and broken when the coil holder I4 is placed or removed from its operative position shown in Figs. 1 and 2.

All the elements of the spiral magnetic tape coil drive and guide arrangement including the magnetic head and the electric circuit interconnectors are thus held in their proper operating position by the holder 24.

The so arranged endless magnetic recordin tape coil holder may be enclosed in a casing of sheet metal, for instance, which is suitably secured, as by screws, to the holder bar 34.

A plurality of such'magnetic recording holders may be stacked one above the other so that the same motor drive and control arrangement may be used for driving and controlling the operation of a plurality of endless magnetic tape, for instance, in the way described in my application Serial No. 524,479, filed February 29, 1944, now abandoned, as a continuation in part of my application Serial No. 340,030 flied June 12, 1940, now Patent No. 2,356,146, dated August 22, 1944.

To this end, a coupling disc 60, similar to the turntable disc 60, may be provided with a shaft 97 having a downwardly projecting portion slidabLv keyed within the hole of the hollow shaft H of the tape expanding disc 30, so as to drive a tape expanding disc 30, similar to that shown in Figs. 1 and 2, when it is placed on the top thereof.

The upwardly facing surface of tape coil holder 24 may be provided with an upwardly facing register socket member 92 and connector member 94 for cooperation with a register member 8|, combined with connector elements of the type shown in Fig. 1, so as to provide bypass connections from all tape holder units stacked up one on the top of the other to a common motor drive and common control arrangements.

If desired, provision may also be made for looking a plurality of stacked up magnetic tape coil holder units in their operating position on the turntable board. To this end, the board 83 and the casing 01 may be equipped with latching elements, such as described in my copending application Serial No. 524,479 filed February 29, 1944, now abandoned, as a continuation in part of my application Serial No. 340,030, filed June 12, 1940, now Patent No. 2,356,146, dated August 22, 1944.

In operating an endless spirally coiled magnetic tape recording arrangement of the type described above, the upper tape guide elements ll should be so held relatively to the tape coil 2| as to permit the tape coil 2| to move substantially without friction relatively thereto, while assuring that the lower edges of the tape coil convolutions maintain frictional engagement with the rotating coil expanding disc 30. The cross-over and aligning rollers 32, 33 should be so mounted and have such inclination as to lift the portion of the cross-over loop rising from the inner coil convolution without interference with any other element of the drive and without subjecting the cross-over loop to any substantial strain. The inner tape coil convolution should be tangentially withdrawn from the periphery of the inner coil guide roller II adjacent the portion of the inner coil convolution 22 which is held down within its position on the expanding disc by one of the radial guide members, and should be similarly brought back to a similarly located point of the outer convolution 22.

The endless tape should be long enough ,to provide for the required looseness between the tape coil convolutions 2| so that they may slip past each other while driven at a uniform linear speed through the magnetic head. The tape coil 2| should be held on a portion of the tape expanding disc 30 which is rotated at a suiiicient speed so as to automatically expand and maintain the tape coil convolutions in a loose condit on.

The tape coil should be wound loose enough so as to provide sumcient slack to eliminate excessive friction. On the other hand, the tape should not be too loose, since otherwise if it should happen to tighten up in one part, it may become excessively loose in another part, and if an excessively loose tape spiral does not find suiiicient space to expand, it may buckle and become kinked. Accordingly, the slack in the tape should not be permitted to be large enough to allow such buckling.

The surface of the tape 29 should be highly polished. The solder Junction or Junctions on the endless tape 20 should be made as smooth as possible, and the soldering Junctions should be only negligibly thicker than the other portions of the tape.

The expanding or spreading of the tape coil 2| brought about by the rotation of the expanding disc 30 automatically tightens the cross-over loop in the desired tension condition, and makes it possible to impel such endless tape coil either by driving the expanding disc or one of the rollers over which the cross-over loop is guided. If a cross-over roller is used for driving the tape, the frictional engagement between the cross-over loop and the cross over roller may be increased by a pressure roller pressing the tape against its periphery.

In the operation of an endless spirally-coiled magnetic recording tape of the type described above, it is important to adjust the driving arrangement so that the tape is maintained loose and at a predetermined desirable tension. This is facilitated by the adjustable mounting of the cross-over roller 3| in the guide channel of the coil holder 33 or by some similar arrangement. The tension of the moving endless tape coil may be addusted to the proper value as follows:

After releasing the clamping screws of the cross-over roller 3|, it is first pulled outwardly so as to increase the tension of the cross-over loop and the moving tape 2| until the coil is tightened and the slippage friction between the tape convolutions stops the motion of the tape. Thereupon, the cross-over roller 2| is gradually moved inwardly so as to progressively release the crossover loop and loosen the tape so that it starts moving, while observing the decrease of the tape tension, for instance, by a tension meter applied to the cross-over loop. The gradual loosening of the tape will gradually decrease the tension of the tape until a condition is reached at which a further release of the cross-over roller does not give a further decrease of the linear tension of the tape. This is the desired condition in which such endless spirally-coiled magnetic recording arrangement should be operated. The cross-over roller should be clamped and locked in the position at which the tape has the so-adjusted tension condition.

' According to one phase of the invention, the tape 20 of a flat-coil endless tape recorder of the type described above is provided with a convexconcavo cross-section, as shown in Fig. 7A, so that its concave surface faces theinterior of the flat tape coil and the tape has a tendency to straighten out and expand its coil convolutions in outward direction.

Fig. 8' shows a modification of the cross-over loop guiding arrangement illustrated in Figs. 1 to 3. A cylindrical guide roller I03 is revolvably held by the holder bar 34 so that its outer periphery is aligned tangentially directly above the underlying circular periphery of the inner rim 3| of the tape inner disc roller 3|, which is engaged by the inner convolution 22 of the tape coil 2|. The inner convolution 22 is tangentially withdrawn from its place along the rim SI of the inner tape coil roller 3| at the point at which it is in tangential alignment with the guide roller I05 and helically guided thereover along the cross over loop passing over two cross-over rollers 32 mounted on an extension of the holder bar 34 to the starting point of the outer convolution 33, as in the arrangement of Figs. 1 and 2.

If very high quality reproduction is desired, the arrangement of Figs. 1 and 2 may be modified in the way shown in Fig. 9. In this arrangement, the cross-over loop 24 of the spiral magnetic tape coil 2| is guided over two rollers Ill, 2 revolvably held by the holder bar 34 in a way similar to the cross-over roller 32 of Figs. 1 and 2. The

' roller 2 is designed so as to have a large inertia,

and a length of the tape is held frictionally coupled thereto, as by means of a belt 3 which is pressed against a portion of its periphery by a plurality of belt guide rollers ||4, suitably supported, as by a bracket mounted on the holder bar 34. The two sides of the cross-over loop extending between the inertia roller "2 and the tape coil 2| are held tightly coupledto the periphery .of the intermediate inertia roller I I l, as by coupling belts 5, held pressed against the opposite peripheral portions of the roller III by belt guide rollers 6.

As in the arrangement of Figs. 1 to 3, the tape expanding disc 30 or the roller 2 which serves as a cross-over roller, drives the tape 23 at the desired uniform linear speed. The inertia roller III to which the sides of the cross-over loop are coupled, serves to isolate the outer portion of the cross-over loop passing over the second inertia roller I I2 from the tape driving disc 30. The side portion of the cross-over loop moving from the, isolating roller toward the inertia roller 2- may be made very loose, and is shown with a freely hanging loop portion I I1.

However, since the portion of the loop which passes through the magnetic head 25 is held firmly coupled to the periphery of the inertia roller 2 which has a relatively large inertia, this loop portion will be impelled through the magnetic head at the peripheral speed of the inertia roller N2, the large inertia of which will equalize fluctuations of the speed transmitted thereto from the driving disc 30.

Figs. and 11 show another form of a flat 76 wall member 23 is shown provided with a hollow 12 endless tape coil magnetic recording device exemplifying the principles of the invention. The convolutions of a substantially flat compact magnetic tape coil 2|, forming part of an endless tape. are held and guided in a horizontal operating position by an upwardly facing guide surface of a circular guide wall member 30-3 in a manner similar to that described in connection with Figs. 1 and 2. The inner convolution 22 of the tape coil 2| is engaged by the periphery of a revolvably mounted circular inner guide disc |3-3 and the inner tape coil convolution 22 is withdrawn from he coil by guiding it along a helical path indicated, for the sake of clarity, in an exaggerated manner in Fig. 10, from its position on the revolvable guide disc 3l-3 over a portion of the adjacent circular cylindrical periphery of a similar stationary circular guide disc 32-3, of the same diameter and mounted adjacent thereto in alignment therewith.

The inner convolution 22 of the tape coil 2|, so withdrawn along a helical path over peripheral portions of the inner revolvably mounted circular guide disc 3|3 and the adjacent stationary circular guide disc 32-3, is then guided over the peripheral guide grooves of two revolvably mounted guide rollers 33-3, 34-3 along the cross-over tape loop 20 past the magnetic transducer heads S-IS, 5-i6, back to the startin point of the outermost tape convolution 23 of the tape coil. The two guide rollers 33-3, 34-3 may form part of a fly-wheel structure designed to maintain the motion of the tape length passing through the transducer head 5-H at a constant speed, suitable means, indicated by spring biased pressure rollers 35-3, being provided to assure eflfective coupling engagement between the fly-wheel rollers 33-3, 34-3 with the portions of the cross-over loop 20 engaged thereby.

The magnetic heads 5-l5, 5-l8 may be of the general type described in the copending application of S. J. Begun, Serial No. 550,573, filed August 22, 1944, now abandoned. It has two wall members 5-l2 which are provided along their exposed edge with an outwardly tapering elon gated guide channel 5-|3, the deepest portion of which has a channel track of a width equal to the width of the tape 20, in the manner described in the application of Williams and Begun, Serial No. 546,808, filed July 27, 1944, now abandoned, in connection with Figs. 10 and 11. Between the two wall members are held clamped the pole piece edge portions of a double-polepiece obliterating head unit 5-l5 and a similar double-pole-piece transducer head unit 5-|6, so that the pole faces of the double-pole-piece unit are exposed along the bottom region of the guide track into operative engagement with the record track moving thereover.

The deepest portion of the portion of guide channel 5-|3 extending between the pole faces of the two double-pole-piece units 5-l5, 5-l6 and adjoining their outer regions are formed by the arcuate surface portions of flat plate members 5-2l, 3-22, held clamped between the two outer wall members 5-l2 of the transducer head. The two wall members 5-H and plate members 3-22, 5-23 may be formed of ceramic material. so that their edge surface shall provide firm positive guide surfaces for the fiat tape moving thereover toward and away from the pole face region of the two double-pole-piece units 5-l5, 5-l3 of the transducer head.

In the arrangement of Figs. 10 to 11, the guide shaft section 25-3 on which is seated the bearing member of the revolvably mounted guide disc 3l-3 and the upper stationary guide disc 32-3. The convolutions of the flat tape coil 2| are held confined in their position within the flat coil layer by a circular cover plate 4l-3 provided with a central raised mounting portion 42-3 having a central mounting hole fitting over the shaft 25-3 and suitably retained thereon as by a nut ring 44-3 threadedly engaging the externally threaded end portion of the hollow shaft 25-3 As shown in Figs. 10 and 11, the cover plate structure 4i-3 is provided with an arcuate slot 46-3 overlying the peripheral range of the stationary guide disc 32-3 to provide a passage for the inner convolution 22 of the tape coil 2| as it is withdrawn from the inner guide disc 3l-3 toward the cross-over loop in the manner indicated in Figs. 10 and 11. The cover plate, 4l-3 is provided with three leg projections 45-3 arranged to engage supports 5l-3 provided on the top wall 50-3 of the recording device. In order to hold the cover plate 4I-3 and the guide disc 32-3 secured thereto in a stationary position, one or more of the top wall supports 5l-3 is designed to form a socket which engages one of the leg projections 45-3 of the cover plate so as to prevent rotation thereof when it is mounted in its position on the recording device as shown.

In the recording device of Figs. and 11, the guide wall member 25 with the cover plate 4i-3 are arranged to form a detachable tape coil holder unit which may be removed from its position on the recording device by lifting it from the centering post $I-3 of a shaft member forming part of a turn-table 60-3 extending above the top wall 53 of the recording device and suitably driven by a turn-table drive mechanism supported on the inner side of the top wall 50-3.

The recording device of Figs. 10 and 11 may be operated in the same manner as the device of Figs. 1 and 2, for instance, by driving the coil supporting disc 25 at a suitable speed so as to impart to the tape coil convolutions of the tape coil 2i outward expanding forces tending to maintain the coil convolutions in loose condition while impelling the cross loop past the transducer head. Alternatively, one of the guide rollers, for instance, guide roller 34-3 may be utilized to drive the cross loop 20 of the endless tape past the transducer head and a suitable driving interconnection is provided to drive the tape coil supporting disc at a speed required in order to impart to the tape convolutions of the tape coil 2! the outward expanding forces which maintain the coil convolutions in the desired loose condition.

Other arrangements than that described above may be utilized for imparting to a fiat coil of an endless magnetic recording tape of a recording device of the type described above outwardly expandingforces required to assure foolproof operation of such flat tape coil endless magnetic recording device. If the flat tape coil of such endless magnetic recording device does not have an excessive number of convolutions, and the exposed tape surface has united thereto a molec ular layer or film of graphite lubricant, a recording device of the general type shown in Figs. 10 and 11 will operate in a foolproof manner even if the coil supporting wall 25 is retained in a stationary position and is aifixed to the cover to form therewith a unitary casing enclosing the fiat tape coil as long as provision is made to impart to the tape coil convolutions 2| outwardly expanding forces.

Figs. 10 and 11 show one manner for imparting outwardly expanding forces to the flat tape coil of an endless magnetic recording device of the foregoing type in which the tape coil supporting disc 25 is affixed to the cover wall 4 I-3 and forms therewith a stationary support for the tape coil. In order to impart to such flat tape coil housed in a stationary casing of the type described above in connection with Figs. 10 and 11 outwardly expanding forces, it is sufllcient to positively impart to the outer convolution of the flat tape coil the linear speed at which the cross loop is withdrawn from the inner coil convolution 22 of the tape coil while making the endless tape of sufllcient length so that the convolutions of the flat tape coil remain in relatively loose condition. Thus, if the outer convolution 23 of the tape coil is subjected to forces tending to expand it and give it a greater periphery, the outer convolution will tend to impart corresponding expanding forces to its next adjacent inner convolution which, in turn, will tend to impart corresponding expanding forces to its next adjacent inner convolution and so on, thereby preventing the cumulative development of frictional slippage forces between adjacent coil convolutions and the resulting large stresses which would stop the motion of the tape.

In the arrangement of Figs. 10 and 11, this is accomplished by using the guide roller 34-3 over which a portion of the cross loop is guided toward the outer tape convolution 23 of the tape coil for driving the cross loop past the transducer head and providing a rail 10-3 having two closely spaced walls within which the tape length 20-3 which is moving from the guide roller 33-4 toward the opening 46-3 in the rim of the cover plate "-3 through which it passes into the outer convolution of the tape coil 2|.

In order to maintain the tape cross loop 20 which periphery of the stationary guide disc 32-3 is I subjected to the braking action of a brake pad 41-3 which is held suitably biased against the cylindrical periphery of the guide disc 32-3 as by a spring arm 48-3, the other end of which is held suitably aflixed to a bracket pin extending from the cover plate "-3.

In the recording device of Figs. 10 to 11, the coil supporting wall 25 and the overlying cover wall 4l-3 form a self-supporting detachable holder structure which holds confined the flat coil ofthe endless tape in its operative position and permits ready removal thereof from its operating position, th cross loop 20 being readily removed from its engagement with the guide rollers 33-3, 34-3 after the idler rollers 35-3 have been swung away therefrom. One flat endless coil housed in such holder unit may thus be readily replaced by another one, it being merely necessary to place the new holder unit on its position on the mounting and supporting posts provided on the top wall of the recording device and the cross loop may be readily threaded over the uide rollers and the transducer head. 0n re-' moving such tape coil holder unit from its posltion, the external portion of the cross loop may be readily stored in the interior space between the walls 25 and "-3 of the holder unit, for instance, by pushing it through the opening 45-3 into the space between the two walls 25 and 41-3.

In Figs. 12 to 14 is shown a more compact form of endless spiral coil magnetic tape recording ar- 15 rangement or the invention, as in the arrangement of Figs. 1 to 3, its spiral magnetic tape coil 2| being held on the revolvably mounted driven expanding disc 30 and its inner convolution 2| being withdrawn from its position on the rim of the independently revolvably inner coil guide roller 3| at the point where the two deflecting pins 53 keep the coil 2| away from the rim 5| to provide clearance toward the crossover loop 24 the other end of which leads to the outer coil convolution 22. High quality operation and great compactness is achieved by mounting an independentlyrevolvably flywheel member I2I in axial alignment with the expanding disc 30 and the inner coil roller 3|, the flywheel I2I and the inner coil roller 3| being shown mounted for independent rotation around the hollow shaft extension II of the expanding disc 30. A holder bar I22- serves as the similar holder bar 34 of Figs. 1 to 3, as the mounting support for all revolvable elements as well as the magnetic head 25.

The crossover loop 24, after being withdrawn. in the direction of its motion from the inner coil convolution 2| adjacent the deflecting pins 53, is led over the crossover roller 32 toward the upper groove of a similar roller I23 mounted on the cross arm 35 of the holder bar 34, the holder bar being led therefrom over loop portion 240:. to the periphery of the flywheel I2I and along one or two downwardly pitched helix loops back over loop portion 24b to the lower groove of the cross arm roller I24 and therefrom at the lower level over the end portion 240 of the crossloop, by way of the aligning roller 33 to its position on the outer coil convolution 23.

As shown in Fig. 12 the inner coil roller 3| and the flywheel I2| run on antifriction members, being provided with suitable ball bearing races and balls which keep them in their operating position and permit them to rotate relatively to each other and to the expanding disc with a minimum of friction.

As shown in Fig. 9, the crossover loop 24 is arranged to move through a lubricant holder 25-I for applying a graphite lubricant to the moving tape, in the manner described in the copending application Serial No. 440,312, filed April 24, 1942, by H. B. Miller, now Patent No. 2,426,838.

Figs. 15 to 18 show another form of endless spirally-coiled magnetic tape recording arrangement. An endless magnetic tape 20 is wound into a spiral coil 2| resting on the upper surface of a .revolvably mounted tape expanding disc I40, and the inner convolution 22 of the tape coil 2 I is led over a crossover loop 24 to the outer convolution of the tape coil, the coil being confined within its position on the disc by radial guide members, as in the previous arrangements.

Above the central portion of the tape coil expanding disc is revolvably mounted an inner guide roller I having a flange at its upper side. The inner convolution 22 of the tape coil 2| is guided away from its inner position on the tape coil expanding disc along a helical path on the inner guide roller and led therefrom over two sets of aligning roller pairs I43 to the peripheral groove of a revolvably mounted driving disc I45, and after passing thereover, the cross-over loop 24 is returned over similar aligningrollers I43 to the starting point of the outer convolution 23 of the tape coil 2|, as in the previous arrangement.

The driving disc I45 is shown arranged to be driven by a turn table drive, and has coupling holes I44 through which it is. coupled to the 6 coupling pin 08 of the turn table disc 50, such as in Figs. 1 to 3.

The driving disc I45 is utilized not only to drive the tape, but also to drive the tape expanding disc I40 at a sufllciently higher speed than the linear speed of the tape, so as to impart to the tape coil 2| held thereon the required outwardly expanding forces.

The expanding disc I40 is shown provided with a downwardly extending grooved belt pulley I41 which is engaged by a rope belt I48, for instance, which also engages the peripheral groove of the driving disc I45 and holds the portion of the crossover loop 24 in its position within the peripheral groove of the driving disc I45. A belt tensioning pulley |5I pivotally mounted and suitably biased by a sprin I52 may be used to keep the belt at the required tension.

The tape coil guide and drive arrangement of Figs. 12 to 18 is likewise designed to form a detachable unit, and all the elements of it, including the magnetic head and electrical circuit connectors, are shown mounted on a holder bar I53, as in the arrangement of Figs. 1 to 3, so that the combined tape coil holding unit may be readily removed from its coupling position on the turn table and exchanged with another, and thus permit selective recording with magnetic tape coils of greater or smaller lengths depending on the requirements. The tape cross loop aligning rollers I43 are shown combined with a revolvably mounted tape retaining roller I44 extending into the groove of the aligning roller so as to prevent the tape from dropping out if it is too loose.

As in the arrangement of Figs. 1 to 3, the tape coil drive and guide arrangement of Figs. 12 to 18 has all its revolving elements carried by a holder bar structure I53 and the tape driving disc I45 is provided with a hollow shaft suitably journaled in a bearing bracket held by the holder bar I53 to make it possible to couple to the top of the tape driving disc I45 of the shaft another turn table disc 60 for driving a similar tape holder unit placed on the top of the tape holder unit.

The radial coil guide members MI 01 the arrangement shown in Figs. 12 to 18 are shown designed so as to retain the tape coil in its desired peripheral operating position on the expanding disc I40 and prevents its expansion or contraction beyond the desired point, and such guide members are intended for use with each of the previously described arrangements.

Figs. 19 and 20 show one form of such radial guide member bars |4| suitable for use in conjunction with a spiral magnetic tape drive of the type shown in Figs. 1 to 3. The outer end of the guide bar carries a stop roller IIiI revolvably .mounted on a pivot stud I62 held on the guide member I4I. The lower end of the stop roller IEI has an inwardly recessed rim portion I63 located above the upper surface of the tape expanding disc 30 and forming a stop limiting the outward expansion of the tape coil, the shoulder portion of the roller IISI preventing upward cligiizoing of the outer convolutions of the tape co In addition, the radial guide member I4I holds journaled on two downward bearing extensions a radial guide roller I64 so that its lower rolling edge shall maintain the lower edges of the tape coil convolutions in frictional engagement with the underlying rotating surface of the tape expanding disc 30.

The radial tape coil guide members I are 17 held in their operating positions by upwardly projecting studs I1I. Each stud "I is slidably held within a sleeve I12 which is clamped by nuts I", I within a radially extending guide channel I16 formed in the overlying portion of the holder structure bar 3l. The lower nut I" has upwardly projecting wings engaging the edges of the channel I16 and the upper nut I15 has a collar fitting within a recess formed in the wall portion adjoining the channel I16, so as to confine all the elements associated with the hold- ,ing structure 3l below its upper level, as in the arrangement of Figs. 1 and 2.

By loosening the clamping nuts I15 of the radial guide bar Ill, it may be shifted in radial direction along the guide channel I16 to different positions depending on the size of the tape coil 2I. A coil spring I11 held in each guide bar support sleeve I12 by threaded stud I13 applies an adjustable pressure to the guide member IlI, so that by turning the stud I16, the pressure with which the guide member I is held against the upper edges of the tape coil convolutions may be adjusted.

Alternatively, if guide bars of the type shown in connection with the arrangement of Figs. 1 to 3 are used for a guide arrangement of the type shown in Figs. 12 to 14, it is merely necessary to provide at their outer ends a revolvably mounted stop roller I 6|, in the way shown in Figs. 22 and 23.

In order to adjust the level of a radial guide bar I ll of the type shown in Fig. 22 relatively to the convolutions of the tape coil 2I, each end of the guide bar I ll may be provided with a stud I3I such as shown at the right of Fig. 22, having the downward thread which engages a suitably threaded hole in the guide bar and the upward oppositely pitched thread engaging adjusting nuts I1l-I and I15I held adjustably against rotation in a channel 19 of the overlying portion of the holder structure bar, in a manner analogous to the corresponding nuts Ill, I15 of Figs. 19 to 21.

As shown at the left of Fig. 22, the end of the radial guide bar I may be held in its adjusted position by a threaded extension of its pivot stud I8I, an internally threaded circular nut I15I, retained in the holder bar channel 19 by a wing nut I1l-I the wings of which are engaged by the channel 19 to prevent it from rotation relatively to the channel. The upper end of the stud I6I may be rotated, as by a screwdriver, to adjust the level of the guide bar I.

By turning as with a screwdriver the upper ends of the studs I8I, the level of each guide bar Ill may be adjusted. Each guide bar I may be adjusted longitudinally along its channel so as to be brought nearer or away from the periphery of the underlying expanding disc by unloosening the clamp nuts I15-I of the associated studs MI and clamping them again in the adjusted position.

Instead of mounting the generally-radially extending guide bars IlI along a radius of the expanding disc 30, it may be held at an angle thereto, in the way shown in the horizontal view, Fig. 23, of the guide bar shown in Fig. 20. When the tap coil 2| is revolved by the expanding disc 36 in counterclockwise direction, such mounting of the guide bars, in the direction inclined to the radial direction of the disc, increases the eflectiveness of the lower edge of the guide bar facing the upper edges of the tape coil convolutions M in assisting the convolutions to be biased in outwardly direction as they are being linearly impelled, while held in engagement with the upwardly facing surface of the rotating expanding disc 33.

In Figs. 24 to 2'1 is shown a self-contained spirally coiled magnetic tape guiding and driving arrangement combined with a magnetic head into a housing unit which may be inter-coupled with a series of similar units to a common motor driving mechanism for selectively recording and reproducing sound on the tape of either one of the units.

On the main wall 3I3 of enclosed by a cover 3 is revolvably mounted a tape driving pulley 3I2 having a driving shaft 3I3 which has on its opposite ends complementary coupling plates 3, 3I5 arranged so as to permit intercoupling of several similar driving pulleys 3I2 located in adjacent casings 3i I, with a similar coupling plate of a motor driven shaft extending from a wall of a casing which houses a driving motor and a control arrangement for controlling the recording and reproducing operations on a magnetic tape of such units.

On another shaft section 3I1 extending from the casing wall 3I6 is revolvably mounted a tape reel 3I9 for guiding in conjunction with the tape driving pulley a long endless magnetic recording tape I3 wound in the form of a multi-layer spiral coil around the tape reel 3I8 and the driving pulley 3I2 in the way shown. A magnetic head I5 and an alignment roller I09 are suitably mounted on the casing wall 3I0 so as to guide the interior layer of the tape I3 from the cira relatively flat casing cular surface 3i! of the tape reel 3I8 through the magnetic head I5 into frictional engagement with the rim of the driving wheel 3I2 against which it is held pressed by a pressure roller 323 which is mounted on a spring biased lever arm arrangement 32l so as to cause the driving wheel 3I2 to drive the inner tape layer 322 through the magnetic head IS in the direction of the arrow 323 at a uniform speed required for satisfactory recording and reproducing of sound.

The end of the inner tape convolution 323 leaving its frictional engagement with the tape driving pulley 3I2 moves over the surface of the pressure roller 320 towards the outer surface of a large cross-over pulley 32l revolvably mounted adjacent the tape coil reel 3I6 so as to guide the end inner tape convolution 322 over its outer surface 325 toward the starting point of the outer convolution 326 of the endless tape coil wound around the tape pulley 3I2 and the tape reel 3I8. The tape driving wheel 3I2 with its pressure roller 326 and the cross-over pulley 32l are so spaced relatively to each other as to permit the tape to move with the required clearance from its innermost layer position 323 to its outermost layer position 326 without imposing excessive strain on any element of the endless tape.

A plurality of radially arranged spreader rollers 333 are mounted in revolving engagement with the opposite edges of the outer tape convolutions surrounding the rim of the tape driving wheel 3I2 so as to keep the outer-tape convolutions of the coil loose and permit them to slip along their adjacent surfaces without excessive friction while the tape driving pulley 3I2 impels the inner tape convolution 322 in the direction of the arrows 323 toward the starting point of the outer tape convolution 326. Each spreader roller has an outer shaft extension 33I journalled in the flanged wail of the casing and a shaft extension 332 journalled in suitable brackets 333 supported by the casing. The inner shaft extension 333 of each spreader roller is suitably driven as by a radially adjustable friction pulley 334 with a rim of friction material, such as rubber, which is pressed against the disc surface of the tape driving wheel 3l2 for rotating the spreader rollers 330 so that they maintain the outer convolutions of the tape coil in loose condition and are free to slip along their adjacent surfaces.

Since the outer convolutions of the tape coil must keep on moving at the speed at which the inner convolution 322 is impelled through the magnetic head, the spreader rollers 33!] are so driven as to assist the outer convolutions of the tape coil to move at the speed of the inner frictionally driven tape convolution without successive friction. To secure optimum operating conditions, a suitable arrangement is provided for adjusting the speed with which the spreader rollers are driven, for instance, by changing the radial position of engagement of the roller driving pulleys 334 with the driving disc of the tape drive ing pulley 3l2. To this end, the roller driving pulleys are so mounted as to permit adjustment of their radial position, for instance, by providing a threaded engagement between the hub of the pulley 334 and the roller shaft 332 and a stop nut 335 so arranged on the shaft that, after adjusting the radial position of the stop nut, the pulley 334 will be kept by the stop nut in a predetermined fixed radial position at which the speed of the spreader roller 330 will maintain the outer convolutions of the endless tape coil in the desired loose condition and permit them to slip past each other without excessive friction.

In an endless tape guiding arrangement of the type shown in connection with Figs. 24 and 25 having tape coils with a large number of convolutions, the spreader rollers 333 may be provided with helical grooves 331, in the way shown in detail in Fig. 25, arranged to keep apart the outer convolutions of the endless tape coil while they slip past each other as they are drawn by the frlctionally driven interior convolution 322 into frictional driving engagement with the rim of the tape driving pulley 3 l2.

While a single motor driven tape driving pulley 3| 2 with its set of spreader rollers 330 as shown in the arrangement of Figs. 24 and 25 will in most cases by itself be able to maintain the entire length of the outer convolutions sufilciently loose so that they may slip past each other without excessive friction, a similar loosely mounted tape driven pulley with a set of spreader rollers may be used instead of the tape reel 8 for guiding the convolutions of the endless tape coil so as to maintain the outer convolutions of the endless tape coils loose and free to move past each other without excessive friction.

In the arrangement described above in connection with Figs. 24 and 25 only the inner tape convolution 322 which is in frictional engagement with the rim of the tape driving pulley 3l2 is subjected to the frictional driving forces. The outer tape convolutions are free to slide past each other along their adjacent surfaces without being subjected to any substantial tension. A relatively long length of endless magnetic steel tape may thus be guided and driven past the magnetic head at a uniform speed for recording and reproducing sound without imposing substantial stresses on any portion of along endless tape. The outer convolutions may be wound sufiiciently loose so that even along the portions at which they are in engagement, the frictional forces are negligible and do not interfere with the motion 20 of the endless tape. Such frictional forces ma be reduced by lubricating the moving tape convolutions, for instance, by-replacingllubricating pads along the path of the tape convolutions.

In endless tape arrangements of the type shown in Figs. 24 and 25 operatingwith a relatively short endless tape requiring only a relatively small number of outer convolutions,the spreader rollers 330 with surfaces of a suitable friction material having no guiding grooves will be able to keep the outer convolutions in the required loose condition.

The required freedom of slippage between the outer convolutions of such endless magnetic tape coil guide and driving arrangement may also be secured by maintaining the convolutions sufliciently lubricated by lubricating pads arranged to lubricate each convolution. Alternatively, an endless magnetic tape coil guiding and driving arrangement of the type shown in Figs. 24 and 25 may be provided with a housing which has a liquid lubricant reservoir and means for feedin the lubricant to the convolutions of the moving tape in a way similar to the construction of oil lubricated anti-friction bearings.

A plurality of separately encased endless coiled magnetic tape sound recording and reproducing units of the type described in connection with Figs. 24 and 25, each provided with suitable coupling means, may be coupled to a common motor drive housed in a similar casing for recording and reproducing sound in the way described in connection with any of the arrangements shown in Figs. 1 to 28. Each magnetic tape coil unit may be provided not only with its individual magnetic head, but also with its individual control arrangement driven through a suitable reduction gearing connected to its motor driven shaft M3. The individual control arrangements may be constructed so as to be operated either manually or by a remote control arrangement.

Another form of endless magnetic tape coilguiding and driving arrangement of the type described in connection with Figs. 24 to 27 is shown in Figs. 28 to 30. In this arrangement the motor driven shaft section 3l3 which is revolvably mounted on the main casing wall 3l0, as in the arrangement of Figs. 27 and 28, drives a pulley member 343 which in turn drives through a belt 3 a tape driving pulley 342 which is revolvably mounted on a shaft 344 suitably secured in the casing wall 3H1.

A disc section 345 Of the motor driven pulley member 343 drives the friction pulleys 334 of radial sets of tape convolution spreader rollers 330 as in the arrangement of Figs. 24 to 27. There is further provided a row of tape guide rollers 34! revolvably mounted on shaft projections 348 extending from the casing wall 3") around the periphery of the motor driven pulley disc 345 so as to guide in conjunction with the tape reel 3|8 located at the opposite end of the casing 3m and the alignment roller I09 associated with the magnetic head l5, as in the arrangement of Figs. 22 and 23, the inner convolution 322 of the endless magnetic tape coil l3 along the outer surfaces of the guide rollers 341 to its point of engagement with the driving surface of the belt driven tape driving pulley 342 against the rim of which it is held by a pressure roller 320 for impelling the inner tape convolution at a uniform speed in the direction of the arrow and causing the end of the inner convolution 322 leaving its engagement with the driving pulley 343 to move over the cross-over pulley 325 to the starting point of the outer conunit. Alternatively,

21 volution 328 in a way similar to the arrangement Fig. 22.

With this arrangement, the driving force imparted by the belt driven tape driving pulley 243 to the end portion of the inner tape convolution 223 draws the tape element of the inner convolutions as it leaves the magnetic head I! over the alignment roller I09, along the guiding surface of the semi-annular row of guide rollers 34'! till the tape element is brought into frictional engagement with the belt driven periphery 343 of the tape driving pulley 342 so that the end of the inner tape convolution 322 leaving its engagement with the tape driving pulley 343 may be deflected over the cross-over pulley 324 mounted adjacent the tape reel M8 on the other end of the coil casing and continue is travel along the outer convolution 326 of the endless coil. An additional set of outer guiding rollers for guiding the outermost convolution 328 of the endless tape coil may be provided along the outer periphery of the tape coil.

As explained hereinbefore, magnetic sound carrier holders of the type described in connection with Figs. 24 to 29, which combine in a self-contained unitary holder structure the carrier guiding and driving means for driving an endless magnetic tape through a magnetic sound transducing head mounted on the holder, are provided with coupling means for detachably coupling such holder to a self-contained power unit comprising a motor mechanism and an amplifier so arranged that upon coupling the coiled sound carrier holder to the power unit, operating connections are automatically established between the motor mechanism of the power unit and the carrier guiding and driving means of the carrier holder, as well as between the amplifier of the power unit and the magnetic head of the carrier holder for recording or reproducing sound in conjunction with the moving magnetic sound carrier. A suitable control arrangement, for instance, of the type described in connection with Figs. 22 to 24, for controlling the recording and reproducing operations on the coiled magnetic sound carriers is combined with the power unit for interchangeable cooperation with the detachable mounted coil carrier holder units.

Such detachable magnetic carrier holder units may be arranged in the way described in connection with Figs. 24 to 29 and provided with double intercoupling means so that a plurality of coiled magnetic carrier holder units may be intercoupled with a common power unit into a unitary magnetic sound recording apparatus and arranged to be selectively controlled by a common control arrangement forming a part of the power each of the coil holder units may have its own remotely actuated control arrangement for independently controlling the recording and reproducing operations thereon.

It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein in connection with specific exemplifications thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific exemplifications of the invention described herein.

I claim:

1. In a magnetic record transducing device for transducing magnetic records, such as recording or reproducing magnetic signals by magnetic flux interlinkage between a magnetic record transequal to said linear speed drivingly engaging at least a portion of the tape moving along the path convolution of said coil for drivsaid layer and forming therewith parts of a substantially rigid detachable holder structure arranged for detachable coupling to a separate unit supplying the tape impelling forces without substantially disturbing the cooperative relation between the coil convolutions and the guide means engaged thereby.

2. In a magnetic record transducing device for ing magnetic record tape: an endless magnetic record tape having a length spirally wound into overlapping tape coil convolutions arranged in a layer and a connection tape length interconnected between the inner convolution and the outer convolution of said coil; guide means including impelling means for guiding and impelling the elements of said tape at a desired linear speed along the path of its coil convolutions in the direction from the inner convolution toward the outer convolution so that a portion or the connection tape length moves past said record transducer means; said guide means comprising a guide member having a generally upwardly facing guide surface member supporting the tape-coil edges on one side of said coil and including a drive element driven at a speed at least equal to said linear speed and drivingly engaging at least a portion of the tape moving along the path of the outermost convolution of said roll for driving said convolution at least at said linear speed and thereby impart to the overlapping convolutions of said tape coil forces tending to expand said coil convolutions so as to maintain the slippage forces between the adjacently moving coil convolutions below a disturbing level; portions of said guide means constituting elements which maintain said coil convolutions confined within said layer and forming therewith parts of a substantially rigid detachable holder struc ture arranged for detachable coupling to a separate motor unit supplying the tape impelling forces without substantially disturbing the cooperative relation between the coil convolutions and the guide means engaged thereby.

3. In a magnetic record transducing device for transducing magnetic records, such as recording or reproducing magnetic signals by magnetic flux interlinkage between a magnetic record transducer means and elements of a relatively moving magnetic record tape; an endless magnetic record tape having a length spirally wound into a tape coil with overlapping tape coil convolutions arranged in a layer and a connection tape length interconnected between the inner convolution and the outer convolution of said coil; guide means including impelling means for guiding and impelling the elements of said tape at a desired linear speed along the path of its coil convolutions in the direction from the inner convolution toward the outer convolution so that a portion of the connection tape length moves past said record transducer means; said tape having a convex concave cross section and being arranged so that its cross section is flattened when wound onto a coil and that its elastic restoring forces tend to expand said coil convolutions for reducing the slippage forces between adiacently moving coil convolutions below a disturbing level.

4. In a magnetic record transducing device for transducing magnetic records, such as recording or reproducing magnetic signals by magnetic flux interlinkage between a magnetic record transducer means and elements of a relatively moving magnetic record tape: an endless magnetic record tape having a length spirally wound into a tape coil with overlapping tape coil convolutions arranged in a layer and a connection tape length interconnected between the inner convolution and the outer convolution of said coil; guide means including impelling means for guiding and impelling the elements of said tape at a desired linear speed along the path of its coil convolutions in the direction from the inner convolution toward the outer convolution so that a portion of the connection tape length moves past said record transducer means; said guide means comprising a guide member having a generally upwardly facing guide surface member supporting the tape-coil edges on one side of said coil and including a drive element driven at a speed at least equal to said linear speed and drivingly engaging at least a portion of the tape moving along the path of the outermost convolution of said coil for driving said convolution at least at said linear speed and thereby impart to the overlapping convolutions of said tape coil forces tending to expand said coil convolutions and tending to maintain the slippage forces between the adiacently moving coil convolutions below a disturbing level.

5. In a magnetic recording apparatus: an endless magnetic record tape; a center disc about which said record material is spirally wound in a coil with overlapping coil convolutions arranged in a layer, and having a cross-over loop connecting the inner and outer record material convolutions, guide means for guiding and impelling the tape at a desired linear speed in the direction from the inner convolution through the cross-over loop toward the outer convolution; magnetic record transducing means located along the path of motion of said tape for recording or reproducing magnetic signal records; said guide means having rotatably mounted guide surface portions arranged so that the edges of the record material convolutions are in engagement with and are guided by said guide surface portions; said guide means including a drive element driven at a speed at least equal to said linear speed drivingly engaging at least a portion of the tape moving along the path of the outermost convolution of said coil for driving said outermost convolution at least at said linear speed and thereby impart to the coil convolutions forces tending to expand said coil convolutions.

6. In a magnetic recording apparatus: an endless magnetic record tape; a center disc about which said record material is spirally wound in a coil with overlapping coil convolutions arranged in a layer, and having a cross-over loop connecting the inner and outer record material convolutions; said center disc forming part of guide means for guiding and impelling the record material at a desired linear speed in the direction from the inner convolution through the cross-over loop toward the outer convolution; magnetic record transducing means located along the path of motion of said record material for recording or reproducing magnetic signal records; said guide means having rotatably mounted upwardly facing guide surface portions arranged so that the edges of the record material convolutions are in engagement with and are guided by said guide surface portions; said guide means including a drive element driven at a speed at least equal to said linear speed drivingly engaging at least a portion of the tape moving along the path of the outermost convolution of said coil for driving said outermost convolution at least at said linear speed and thereby impart to the coil convolutions forces tending to expand said coil convolutions.

7. In a magnetic recording apparatus: an endless magnetic record tape; a center disc about which said record material is spirally wound in a coil with overlapping coil convolutions arranged in a layer and having a cross-over loop connecting the inner and outer record material convolutions, guide means for guiding and impelling the tape at a desired linear speed in the direction over loop toward the outer convolution; magnetic record transducing means located along the path of motion of said tape for recording or reproducing magnetic signal records; said guide means 6 having rotatably mounted guide surface portions arranged so that the edges of the record material convolutions are in engagement with and are guided by said guide surface portions; said guide means including a drive element driven at a speed at least equal to said linear speed drivingly engaging at least a portion of the tape moving along the path of the outermost convolution of said coil for driving said outermost convolution at least at said linear speed and thereby impart to the coil convolutions forces tending to expand said coil convolutions; portions of said guide means constituting elements which maintain said coil convolutions confined within said layer and forming therewith parts of a substantially rigid de- 60 tachable holder structure arranged for detachable coupling to a separate drive unit supplying the tape impelling forces without substantially disturbing the cooperative relation between the coil 5 bcgnvolutions and the guide means engaged there- 8. In a magnetic recording apparatus: an endless magnetic recording tape having a length spirally wound into a tape coil with overlapping tape coil convolutions arranged in a layer and 10 a connection tape length interconnected between the inner convolution and the outer convolution of said coil; guide means including impelling means for guiding and impelling the elements of said tape at a predetermined linear speed along 75 the path of its coil convolutions in the direction from the inner convolution through the cross- 

